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I finally decided to build my very own battery operated GPS device. So I started designing the PCB and i am having hard time understanding certain things.

Here are the details of the board

  • 2-Layer board.

  • Contains GPS receiver and Bluetooth 4.1

  • Battery Management unit ( with charging current of 2A )

  • A Buck-Boost Converter ( 1.6Mhz, ILmax= 1.2A)

  • Controller with 32Mhz Crystal

    How do I decide if I need a Polygon pour? Should the poly always be ground? How does poly affect the performance of the GPS or BLE?

Thanks

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    \$\begingroup\$ Sounds like a pretty complicated board for your first attempt. Be prepared for multiple respins. \$\endgroup\$ – Matt Young Mar 8 '16 at 4:52
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    \$\begingroup\$ In most cases, polygon pour helps. However if there is an antenna, you need to be a little careful. Not only about polygon pour but complete PCB layout as a whole might affect the performance of BT and GPS. Also there are cases where you don't want a single pour for whole PCB. For ex - When analog and digital circuit are present together. If you post the board layout, people here will be able to guide you into right direction much comfortably. \$\endgroup\$ – Whiskeyjack Mar 8 '16 at 4:55
  • \$\begingroup\$ @Whiskeyjack will be posting it ASAP \$\endgroup\$ – R. Hirur Mar 8 '16 at 5:08
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In general, polygon pours are used for ground and power rails. It depends on the layout and the requirements of the circuit. They are "just" copper and they can be used for many purposes: electrical connection, grounding, thermal relief, reference plane for a controlled impedance track, inter-plane coupling...

They can affect the performance of the GPS and BL as any other layout feature. They are part of the whole layout.

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Regarding your project, it sounds kind of complex PCB.

Before thinking about polygon pours you should sketch a first schematics and then start to think about the PCB.

Some questions that may help for the PCB design:

  • How many power rails do i need?

  • What are the power requirements of each power rail?

  • Do I have a fine pitch packages like BGA or QFN? How many layers do I need to fan out these packages?

  • Do I need any controlled impedance track for the RF section?

Probably you would need 4 layer PCB and consider controlled-impedance tracks.

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  • \$\begingroup\$ +1 for mentioning controlled impedance. At the frequencies used they would definitely be a good idea \$\endgroup\$ – DerStrom8 Nov 3 '16 at 11:44

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